Optical imaging system

Abstract

An optical imaging system includes a first lens having an object-side surface that is convex; a second lens having a refractive power and a refractive index of 1.65 or more; a third lens having a refractive power; a fourth lens having a refractive power and an object-side surface that is convex; a fifth lens having a refractive power; a sixth lens having a positive refractive power; and a seventh lens having an object-side surface that is convex, wherein the first lens through the seventh lens are sequentially disposed in numerical order from an object side of the optical imaging system toward an imaging plane of the optical imaging system, and two or more of the first lens and the third lens through the seventh lens have a refractive index of 1.6 or more.

What is claimed is: 
     
       1. An optical imaging system, comprising:
 a first lens having positive refractive power, and a concave image-side surface in a paraxial region; 
 a second lens having a negative refractive power; 
 a third lens having a convex object-side surface in a paraxial region thereof; 
 a fourth lens having a refractive power; 
 a fifth lens having a refractive power; 
 a sixth lens having a convex object-side surface in a paraxial region thereof; and 
 a seventh lens having negative refractive power, 
 wherein the first to seventh lenses are sequentially disposed in ascending numerical order from an object side of the optical imaging system toward an imaging plane of the optical imaging system, 
 wherein the optical imaging system comprises a total of seven lenses with refractive power, 
 wherein a thickness of the fourth lens is greater than a distance from an image-side surface of the third lens to an object-side surface of the fourth lens, 
 wherein a distance from an image-side surface of the fourth lens to an object-side surface of the fifth lens is greater than a thickness of the second lens, 
 wherein a radius of curvature of an object-side surface of the second lens is greater than a radius of curvature of an image-side surface of the first lens, 
 wherein a radius of curvature of an image-side surface of the fourth lens is greater than a radius of curvature of an object-side surface of the third lens, and 
 wherein a refractive index of the second lens is 1.65 or greater. 
 
     
     
       2. The optical imaging system of  claim 1 , wherein the first lens has a convex object-side surface in a paraxial region thereof. 
     
     
       3. The optical imaging system of  claim 1 , wherein the second lens has a convex object-side surface in a paraxial region thereof. 
     
     
       4. The optical imaging system of  claim 1 , wherein the fourth lens has a convex object-side surface in a paraxial region thereof. 
     
     
       5. The optical imaging system of  claim 1 , wherein the fifth lens has a concave object-side surface in a paraxial region thereof. 
     
     
       6. The optical imaging system of  claim 1 , wherein the seventh lens has a convex object-side surface in a paraxial region thereof. 
     
     
       7. The optical imaging system of  claim 1 , wherein the seventh lens has a concave image-side surface in a paraxial region thereof. 
     
     
       8. An optical imaging system, comprising:
 a first lens having positive refractive power, and a concave image-side surface in a paraxial region; 
 a second lens having a negative refractive power; 
 a third lens having a convex object-side surface in a paraxial region thereof, and a concave image-side surface in a paraxial region thereof; 
 a fourth lens having a refractive power; 
 a fifth lens having a refractive power; 
 a sixth lens having a convex object-side surface in a paraxial region thereof; and 
 a seventh lens having negative refractive power, 
 wherein the first to seventh lenses are sequentially disposed in ascending numerical order from an object side of the optical imaging system toward an imaging plane of the optical imaging system, 
 wherein the optical imaging system comprises a total of seven lenses with refractive power, 
 wherein a thickness of the fourth lens is greater than a distance from an image-side surface of the third lens to an object-side surface of the fourth lens, 
 wherein a distance from an image-side surface of the fourth lens to an object-side surface of the fifth lens is greater than a thickness of the second lens, 
 wherein a radius of curvature of an object-side surface of the second lens is greater than a radius of curvature of an image-side surface of the third lens, 
 wherein a refractive index of the second lens is 1.65 or greater, and 
 wherein 55<V7, where V7 is an Abbe number of the seventh lens. 
 
     
     
       9. The optical imaging system of  claim 8 , wherein the first lens has a convex object-side surface in a paraxial region thereof. 
     
     
       10. The optical imaging system of  claim 8 , wherein the second lens has a convex object-side surface in a paraxial region thereof. 
     
     
       11. The optical imaging system of  claim 8 , wherein the fourth lens has a convex object-side surface in a paraxial region thereof. 
     
     
       12. The optical imaging system of  claim 8 , wherein the fifth lens has a concave object-side surface in a paraxial region thereof. 
     
     
       13. The optical imaging system of  claim 8 , wherein the seventh lens has a convex object-side surface in a paraxial region thereof. 
     
     
       14. The optical imaging system of  claim 8 , wherein the seventh lens has a concave image-side surface in a paraxial region thereof.